It is known that the addition of Si-bonded hydrogen to an aliphatic multiple bond, which is described as hydrosilylation, can be promoted by transition metal catalysts, in particular platinum compounds. EP-A-546 716 describes platinum centers bonded to polysiloxane resins via amino groups and use thereof as heterogeneous hydrosilylation catalysts. Heterogeneous catalysts have to be removed from the product after the reaction, since they impair the product's properties such as transparency and mechanical properties.
Polysiloxane-bonded platinum catalysts for hydrosilylation are known from U.S. Pat. No. 3,795,656. According to the process described therein, chloroplatinic acid is reacted with organosilicon compounds having functional amino groups to give organosilicon compounds containing ammonium-platinum(IV) adducts. These organosilicon compounds possess a strongly polar salt-like structure and for lumps or set solid if they are present in pure form. They can therefore be re-dispersed only with great difficulty and can be homogeneously incorporated in silicones as solutions. Furthermore, the preparation of these organosilicon compounds from strongly polar chloroplatinic acid and a weak polar amino-functional organosilicon compound is problematical because of solubility differences. U.S. Pat. No. 4,398,010 describes the reduction of the above organosilicon compound containing ammonium-platinum(IV) adducts, the platinum(IV) centers being reduced to the oxidation stage zero in the presence of bases. The reduction gives solids which can be used as homogeneous hydrosilylation catalysts only as solutions.
C. Hu et al., J. Organomet. Chem. 1986, 307 (1), 115 describe platinum complexes intended for chemotherapy for the treatment of cancer, which complexes have ethylendiamino-functional silanes or disiloxanes and Cl as ligands. The salt-like potassium tetrachloroplatinate is used as starting material in the synthesis and is carried out in water. The process fails when non-polar relatively high-molecular weight aminofunctional siloxanes are used.